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Zs readings over limits
Former Community Member
Doing an EICR in a block of flats and quite a few of the lighting circuits have excessive Zs readings. All the circuits are on 60898 C10's without RCD protection with readings in the late 2 early 3 ohm range (max permitted 2.19). I know test result fails are generally a code 2 but these are LED panel downlighters with mostly class 2 drivers connected via choc boxes above the suspended ceiling so nothing really accessible. They would all comply with a C6 btw. Just wondered if you'd C2 this resulting in an unsatisfactory EICR
under fault conditions ADS has to work to prevent anyone getting an electric shock but what would you code a standard class 2 lighting pendent that had no earth connected? there are no exposed conductive parts on the circuit to get a shock from, the Zs test was made on the unterminated cpc of the T&E cable at the end of the circuit.
I can see the point that it could (in theory) be declared a double/reinforced insulation circuit - and the c.p.c. omitted altogether and Zs would be irrelevant (as it's in a common area, rather than domestic, the bit about ensuring adequate supervision could perhaps be complied with).
With a c.p.c. present however there would seem to be a risk of a L-c.p.c. fault (especially with T&E where the c.p.c. isn't insulated as if it were a live part), which although wouldn't make any exposed-conductive-parts on that circuit live (as there aren't any) - it would make the c.p.c. itself hazardous live - and so too anything connected to it - e.g. exposed-conductive-parts of other circuits connected to the same DB for instance. Granted the touch voltage on remote parts would likely be much lower than at the fault - but if the disconnection time is really extended that still might not be sufficient to ensure safety.
under fault conditions ADS has to work to prevent anyone getting an electric shock but what would you code a standard class 2 lighting pendent that had no earth connected? there are no exposed conductive parts on the circuit to get a shock from, the Zs test was made on the unterminated cpc of the T&E cable at the end of the circuit.
I can see the point that it could (in theory) be declared a double/reinforced insulation circuit - and the c.p.c. omitted altogether and Zs would be irrelevant (as it's in a common area, rather than domestic, the bit about ensuring adequate supervision could perhaps be complied with).
With a c.p.c. present however there would seem to be a risk of a L-c.p.c. fault (especially with T&E where the c.p.c. isn't insulated as if it were a live part), which although wouldn't make any exposed-conductive-parts on that circuit live (as there aren't any) - it would make the c.p.c. itself hazardous live - and so too anything connected to it - e.g. exposed-conductive-parts of other circuits connected to the same DB for instance. Granted the touch voltage on remote parts would likely be much lower than at the fault - but if the disconnection time is really extended that still might not be sufficient to ensure safety.
